1. Field of the Invention
The present invention relates to a document illuminating apparatus in which a document disposed on a document table is illuminated with an illuminating lamp, and the light reflected from the document is made incident on an optical path changing mirror so as to be led to a photosensitive section.
2. Description of the Related Art
Projecting and/or recording systems, which enable an image to be recorded on a predetermined frame of a photosensitive film and which also permit the recorded image to be projected or copied, have already been proposed in, e.g., U.S. Pat. Nos. 3,964,828, 3,972,610, and 4,600,291 and U.S. Ser. No. 632,222, now U.S. Pat. No. 4,619,519 and U.S. Ser. No. 920,336 filed Oct. 17, 1986.
This type of system is so designed that an optical path changing mirror faces diagonally a document disposed on a document table to lead the light reflected from the document to a photosensitive section in order to reduce the size of the system.
To illuminate the document and allow the light reflected therefrom to be incident on the optical path changing mirror, a linear illuminating lamp is disposed at a position intermediate between the document table and the mirror in such a manner that the lamp extends along one lateral side of these members. For example, such a case is disclosed in U.S. Pat. No. 3,697,176. As disclosed in the Patent, however, if the lamp is disposed at a position close to the document table, the illuminance is made uneven on the document. Accordingly, the illuminating lamp must be disposed at a position which is relatively remote from the document in order to illuminate it uniformly with direct rays of light emitted from the illuminating lamp alone. There is one example where the lamp is disposed at a position remote from the document table in U.S. Pat. No. 4,461,566, but this impedes minimization of the size of the system.
To overcome such disadvantage, an arrangement has been devised in which the light emitted from the illuminating lamp is divided into direct rays and reflected rays which have a lower illuminance than that of the direct rays, and these two types of light are applied to the document to make the luminous intensity uniform and allow the illuminating lamp to be disposed at a position relatively close to the document.
However, the above-described arrangement still involves unevenness in the intensity of illumination. Namely, since the optical path changing mirror faces the document diagonally, portions of the mirror on the respective sides thereof which are closer to and remote from the document have different luminous intensities. Such unevenness in the illuminance is particularly noticeable at portions of the document which are illuminated with that part of the light from the illuminating lamp which has been reflected for the purpose of lowering the illuminance.